Continuous research is underway to solve depletion of petroleum resources and environmental pollution due to continuous industrialization. To this end, alternative energy, especially as eco-friendly energy has been developed. Ethanol as alternative energy resource under great interest has already been used as a solvent or base material in many fields, and its potential for use as an eco-friendly fuel mixed with gasoline has also been studied (Licht F. O. “World Fuel Ethanol, analysis and outlook”(2006)). There is a lot of research on a method for effectively producing not only ethanol but also other alcoholic compounds, especially methanol compounds.
Although a method using biomass is a main method for conventionally producing ethanol, it is costly to perform processes and a conversion rate is not so good. A catalyst process for directly synthesizing ethanol using syngas has been developed as an alternative to the method using biomass. However, also the direct ethanol synthesis process is inefficient because of a high selectivity of not only ethanol, as a main product, but also by-products. Further, the direct ethanol synthesis process has a disadvantage of high production cost because of using platinum or rhodium (J. Catal. 261 (2009), 9-16).
In a method for indirectly synthesizing ethanol, dimethyl ether (DME) is firstly produced by using syngas, and methyl acetate (MA) is secondly produced by a carbonylation of the dimethyl ether, and then the methyl acetate is hydrogenated to obtain ethanol finally. In this connection, it is efficient to use a zeolite catalyst for the carbonylation reaction of dimethyl ether for producing the methyl acetate. Especially, a crucial acetyl-group based intermediate generated in an 8-membered oxygen ring pore of a mordenite zeolite structure including the 8-membered oxygen ring pore and a 12-membered oxygen ring pore is activated in the carbonylation reaction of the dimethyl ether (Angew. Chem. 45 (2006) 1617-1620, J. Catal. 245 (2007)110-123, Korean Patent Registration No. 10-1391571).
However, the mordenite zeolite has a high selectivity at a low temperature, but it has a disadvantage in a conventional aspect in that the mordenite zeolite as the catalyst is inactivated rapidly. Further, from the conventional researches which have been conducted under mild conditions in which a molar ratio of carbon monoxide (CO) and dimethyl ether is 45:1 or above, a high conversion rate and the high selectivity are only natural results. However, there is a limit to solve problems of rapid inactivation of the catalyst due to coke generated in the actual reaction, and generation of hydrocarbon as a by-product.